Rotation Script moves linked objects

I have created a rotation script which causes a linked object to rotate 90 degrees one way as if winding up then release and rock back to it's starting point. After a pause the whole script resets. The behaviour is great but if I leave the object sitting around running the script for a few hours it tends to drift from it's starting position. Over a day it moves maybe a 1/2 meter.

This is an example of my rotation

rotation Y_rot = llEuler2Rot( < 0, -5 * DEG_TO_RAD, 0 > );

for( i = 1; i < 19; i++ )
{

rotation newRotation = Y_rot * llGetRot();

llSetRot( newRotation );
}

Can anyone help with this problem?

Yes. its accumulating floating point errors.
Try this.
When first Rezzed, have the object query and remember its exact position on the grid. (x,y,z) coordinates.
then, once an hour or once a minute, or once every 100 times through your loop, have it reposition itself to the stored location.
(frequency of this depends on how often you are calling the rotation, and how far and fast its drifting.)

Thanks Sterling. Wish I'd thought of that earlier. Working great now. I just reset the position every iteration of the script. Works great now